The invention relates to a consolidated winding electrical capacitor having a circular, oval, or flat cross-section of dielectric bands of stretched plastic films or sheets wound with one another and each provided with a regenerably thin metal layer as a coating. The coatings, alternating from band to band, extend to different edges and form surfaces at which the antipolar coatings are connected to one another by schoopageapplied metal layers serving the purpose of contacting, and to which power leads are secured.
The invention further relates to a method for the manufacture of such an electrical capacitor wherein bands of stretched plastic films or sheets are metallized on one side at least up to one edge. The bands act as a dielectric and, in particular, have a wavy cut at the edge, and are wound onto a winding spindle having a circular, oval, or flat cross section. The winding thus fashioned is then freed from the winding spindle under given conditions and the wound capacitor which has thus arisen is provided with end contact layers.
Electrical wound capacitors of this type and methods for their manufacture comprising the above-specified method steps have been known for many decades. They have been employed as stretched plastic films, films of polycarbonates, polyethylene terephthalate, or propylene. The application of the metal layers to the two end faces which serves the purpose of contacting the individual coatings occurs by means of the widely known schoopage method.
German OS No. 33 42 329, corresponding to U.S. Pat. No. 4,563,724 incorporated herein by reference, describes an electrical capacitor of a consolidated stack of dielectric layers of plastic films layered on top of one another. Each is provided with a metal layer as a coating. It has an incision at one narrow side. As a consequence, the individual dielectric layers are provided with projections on which, alternating from layer to layer, the coatings are interrupted by insulating strips. Thus, the metallizations situated on the surfaces formed by the projections connect antipolar coatings to one another in alternating fashion. The method set forth in U.S. Pat. No. 4,563,724 provides that metallized plastic bands with correspondingly arranged, intermittent metal-free strips are provided which are subsequently wound onto a drum. Thus, the incisions are produced in the resulting mother capacitors, and the individual stacks are subsequently parted from the mother capacitors.
The electrical layer or stacked capacitor of U.S. Pat. No. 4,563,724 has an extremely low induction because the current paths over the metal coatings, through the dielectric and onto the antipolar coatings, proceed in opposite directions so that these current paths are compensated, and thus cannot produce a magnetic field (induction).
Previously known low-induction wound capacitors have their dielectric formed, in particular, of stretched polystyrol, and coatings which are in the form of self-bearing metal foils which are wound with the polystyrol films. In order to achieve low inductance, the external power feed elements are connected to the metal foils such that the current paths in the metal foils mutually compensate. For example, the power feed to one metal foil is connected as close as possible to or in the center of the winding, and the other power feed is connected to the other metal foil at the periphery of the winding (bifilar format).
Low-induction electrical wound capacitors having dielectric bands on which a regenerably thin metallization is applied are either unknown or have not enjoyed application in practice.